So if you have a Blizzard account you can NOW and upto december 3th get SC2 base game for free.
If you already own the base game you can instead get the first addon "heart of the swarm" for free.
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If you already own that the rumour says you get something else but not sure what or when this will happen.. will update when i get confirmation on what..

well.. for the US ppl maintenance and patching is in the works right now so it is not rdy..
For EU ppl we haveto wait for US to finish and then we are nxt..
so don't panic if you haven't gotten any free shit yet :)